The oil light is always on in my 2006 VW Golf 1.4i. I have tried changing the oil pump, oil switch, and even putting more oil in, but the light remains on.
There are only a few possibilities:
- Oil pressure is actually low.
- The light is overloaded with meanings and it is trying to tell you something else.
- There is a faulty component.
- There is a fault in the circuit.
The first thing to do is to make sure you understand what the light is trying to tell you. For example is the light solely a pressure monitor or could it also be a service reminder as well. The owners manual will tell you this.
Next see if you can find a schematic of the light circuit. It will be in the Bentley manual for the car if no place else. That will give you the definitive answer about what causes the light to come on.
Armed with that knowledge, verify that things are working as you think they should. For example, does the oil pressure switch actually seem to work (pull the connector off and hook a meter to it and see if it changes state when you start the engine). You could also pull the pressure sensor and connect a gauge to see what the pressure actually is.
Once you have come this far the only remaining possibility is a short in the wiring. Assuming the oil pressure was good. If the engine has enough time in it if is possible that the bearings are worn enough that the pressure is actually low. A really dirty oil filter might also cause low oil pressure.
Definitely should get the cars fault code memories read. Ill bet this will provide you an actual informational message about the meaning. It could just be a faulty oil level sensor, but its guesswork unless you know what the car is actually telling you. These cars use a databus and pass binary messages between electronic control units so getting wiring diagrams wont help. You could try owners forums in your area and post a request for someone to do a VCDS scan for you.. Or failing that pay the dealer to do so.